Blood processing systems are used for a range of purposes. They are used, for example, to collect blood from donors, for autotransfusion where blood lost by a patient during an operation is collected, cleaned and reintroduced into the patient's circulatory system, to prepare collected blood for freezing, to deglycerolize frozen thawed red cells, for washing red blood cells and for washing frozen thawed platelets.
There are features which would be very desirable with virtually all blood processing systems but are not provided by current systems. To understand these desirable features one must first fully appreciate the practical aspects of the blood processing technology as discussed below. The desirable features are small size of equipment, acceptably priced disposables, automatic operation, protection from operator error, protection from equipment error, speed of operation and complete one-step processing.
Considering first a blood collection system, the collection of blood from donors takes place both at blood banks and via use of mobile units during so-called blood drives with the mobile unit collection often exceeding that at the blood banks. Accordingly, it is desirable to have relatively compact systems so that a larger number can be easily transported to the site of blood collection. Fast blood collection is desirable since if donor comfort is increased by reducing the donation time it is easier to attract donors.
Whole blood has usually been collected from a donor via gravity flow; alternatively, use of a blood removal roller pump has been used to aid collection from a donor. The whole blood was then transported to a blood processing facility and centrifuged to separate the plasma from the erythrocytes. In some instances a leukocyte filter was used on the whole blood or on red cells to reduce the chance for undesirable patient reactions to donor leukocytes when donor red cells were later transfused into a patient. This whole blood collection procedure suffers from a number of drawbacks. One major drawback is that the procedure is highly dependent on the skill of the operator taking the blood donation, thus requiring extensive and expensive training of operators. Also, the current procedures require nearly constant operator attention, thereby limiting the amount of blood which can be safely collected in a given time period; i.e., the operator can only safely oversee a limited number of blood donations at any one time. There is also a drawback that having several people handle the whole blood as it is collected and separated into its component parts increases the chance of operator error. Another drawback is that the several steps required, even if carried out by a single operator, increase the risk of contamination of the whole blood and of its separated component parts.
An apparatus has also been proposed which has the capability of fully processing blood at the collection site but it is relatively bulky and requires the use of a built in rotating centrifuge. The apparatus has a number of limitations which include cost, relative bulkiness, the possibility of leaks at rotating seals, relatively slow speed since all blood must be collected prior to the beginning of separation into components, etc., and the requirement of close operator supervision. The apparatus is disclosed in U.S. Pat. Nos. 5,651,766; 5,728,060; and 5,733,253.
Another blood processing system, called an intraoperative autotransfusion system, is commonly used during certain operations, such as orthopedic surgery and open-heart surgery, when a great deal of blood can be lost by the patient. In autotransfusion the lost (shed) blood along with air, particulate matter and diluting solvents are collected. The air, solvents, and particulate matter are removed. The cells are washed and the hematocrit is increased to a desired level such as that normally present in the body (about 40%). The resulting blood-cell suspension is transfused back into the patient. Autotransfusion reduces the cost and problems (incompatibility and infection) associated with blood bank blood. It would be desirable to have a relatively small size unit since operating rooms constitute a highly crowded environment. Furthermore, automatic operation is desirable as it allows medical personnel to attend to other matters while the autotransfusion unit carries out the desired task of collecting and cleansing red blood cells for re-infusion. Low cost of disposables is necessary since if the cost is too high even the technically best available system may not be used. The system set forth in U.S. Pat. Nos. 5,242,384 and 5,423,738 is adapted for automated autotransfusion but the high cost of the complex disposable and its tangential flow separator has prevented this system from wide commercial acceptance.
Another type of blood processing system is the thawed blood processing system. It is intended to remove glycerol and free plasma hemoglobin from thawed frozen red blood cells. It is primarily used by the military on land and aboard ship to provide red cells in emergency situations. The military has stockpiled a large number of units of blood, all of one universal donor type, for this purpose. Frozen blood is also commonly used when a patient undergoing elective surgery desires to stockpile his or her own blood for use during the surgery. Frozen blood is also used to supply rare blood types.
One of the problems with using frozen blood is that it requires that some type of agent be added to the red blood cells to allow them to be safely frozen; glycerol has commonly been used for this purpose. Also, some red blood cells are damaged by the freezing process. Once thawed, these damaged red blood cells release free plasma hemoglobin. Both the glycerol and free plasma hemoglobin must be reduced to safe levels in the thawed blood and saline and a red cell storage solution must be added to the thawed blood before transfusion into a patient. Once again, small size, automatic operation and low cost are important factors.
Another blood processing system is used for washing red blood cells. Blood is collected, separated into its components and concentrated red blood cells are stored in a bag which contains the storage solution to preserve the red cells. Once again, small size, automatic operation and low cost are important factors.
A further blood processing system is used to wash frozen thawed platelets. In this system the platelets are frozen with, for example, DMSO, and possibly other preservatives. When the frozen platelets are thawed, the DMSO and possibly other preservatives are preferably washed from the platelets before the platelets can be used.
U.S. Pat. Nos. 5,670,312; 5,460,493; 5,311,908; 5,273,517; 5,195,960; 4,985,153; and 4,385,630 disclose various types of blood processing systems and system components.